Short-term dietary antibiotics altered the intestinal microbiota and improved the lipid metabolism in hybrid grouper fed medium and high-lipid diets

The increasing aquaculture production brought about the extensive use of high-lipid diets and antibiotics as effective means to spare costly protein and treat diseases, respectively. However dietary antibiotics and high-lipid diets both influence the gut microbiome . We hypothesized that antibiotics could affect the lipid metabolism by altering the composition of intestinal microbiota in fish at medium- and high-lipid diets. We explored this hypothesis by a 6-day administration of antibiotics mixtures to the diet of hybrid grouper ( Epinephelus fuscoguttatus ♀ ×  E. lanceolatus ♂). Four diet groups were designed: medium-lipid (control diet, CD, 8.27% lipids), CD supplemented with antibiotics (vancomycin, neomycin sulfate, metronidazole ; ACD), high-lipid diet (HD, 15.32% lipids), and HD with antibiotics (AHD). The ACD and AHD groups exhibited significantly decreased crude lipids, lipid droplets, triglycerides , and total cholesterol contents of the liver (compared to CD and HD). The antibiotics treatment mainly upregulated the expressions of genes associated with lipolysis at the medium-lipid diet and downregulated the expression of lipogenesis-associated genes at the high-lipid diet. The antibiotics treatment mainly inhibited the expression of lipogenesis-associated proteins in the high-lipid diet, and mainly facilitated lipolysis in the medium-lipid diet. The antibiotics treatment significantly reduced the abundance and diversity of microbes, the abundance of Firmicutes , and Firmicutes / Bacteroidetes ratio. In addition, antibiotics homogenized the intestinal microbiota, which in turn caused analogous effects in medium- and high-lipid diets in grouper. In conclusion, short-term dietary antibiotics treatment improved the accumulation of lipids and lipid metabolism by inhibiting lipogenesis at the high-lipid level and facilitating lipolysis at the medium-lipid level via affecting the composition, diversity and functional pathways of gut microbiota.